The present invention relates to an automated data transmission system for the periodic transmission of acquired data from a communication system installed at a remote location to a central station via a telephone line.
The development of data transmission systems employing modems to transmit and receive coded data via telephone lines has lead to the development of various types of applications of this technology. Among these is a communication system for transmitting energy consumption data from electric utility meters to centralized data collection stations, thereby obviating the need to periodically send a meter reader to the metered location. Such a system requires a meter equipped with an electronic register containing a CPU and a suitable memory. Such registers are presently marketed by the Westinghouse Electric Corporation under the tradename EMF 2000.
U.S. Pat. Nos. 4,241,237 and 4,455,453 disclose systems for transmitting electric utility meter readings from a remote location to a central station via a telephone line. To establish a connection, a call is initiated to a preprogrammed telephone number from the remote location at a scheduled time and meter data is then transmitted. These patents propose the provision of two sensors for monitoring two different functions. At the completion of a transmission, the central station transmits instructions informing the remote location of the next scheduled time for establishing a connection.
Since such a system will normally share a telephone line with conventional telephone instruments, each transmission constructed by the system should have a short duration. This requirement imposes a significant restriction on the amount of data which can be collected and transmitted, with the result that the practical value of such a system is limited.